Microelectronic devices can be shipped in a packaged format or an unpackaged format. Packaged microelectronic devices typically include a semiconductor chip, a lead frame, and a protective plastic shell. In one application, the chip has a plurality of bond pads that are electrically coupled to pins of the lead frame. The chip and the lead frame are then encapsulated in the plastic shell, and the pins are generally bent into a desired configuration. Another type of packaged device is a ball grid array. Unpackaged devices can include CSP (Chip Scale Processing) and KGD (Known Good Die) products in which the chip is not encapsulated in a plastic shell. The packaged and unpackaged devices are typically called “IC devices” or “microelectronic devices.”
During processing of IC devices, a large number of devices are generally placed in a tray or other container for protection. JEDEC trays, for example, are used in the microelectronic device manufacturing industry to hold memory devices and other types of IC devices. JEDEC trays have a plurality of parallel slots to hold several rows of individual IC devices. The IC devices are often transported between processing machines or stored in the JEDEC trays. For example, IC devices are transported between burn-in ovens, electrical testing machines, marking machines, scanning machines, and the final packaging machines that load the IC devices onto shipping trays, continuous tapes or into tubes.
Several JEDEC trays with a large number of IC devices are generally stacked on each other so that a large batch of IC devices can be stored, transported and processed. In one conventional application for handling JEDEC trays, a disposable band or strap is used to bind several loaded JEDEC trays together and form a tray stack. An empty JEDEC tray is often placed on top of the tray stack to retain the IC devices on the next lower JEDEC tray. To separate the JEDEC trays for processing or testing the particular IC devices, the band is cut or otherwise removed from the tray stack. The individual IC devices are then processed. After the individual IC devices have been processed, they are reloaded onto a JEDEC tray (if they were unloaded), and then the trays are restacked and rebanded into a secure tray stack.
The procedure of banding together a stack of JEDEC trays suffers from several drawbacks. One drawback is that the tray stack can be dropped or jostled before it has been banded. Another drawback is that the banding machine may bend or break the trays. Both of these drawbacks typically result in damaging all, or at least some, of the IC devices in the tray stack. Still another drawback of banding JEDEC trays together is that the banding procedure is time consuming, and it is also cumbersome to stack the banded tray stacks upon each other. A further disadvantage of banding JEDEC trays together is that problems arise in tracking the tray stacks because identification labels attached to the tray stacks can fall off or be placed on the incorrect tray stacks. Therefore, banding JEDEC trays together is not a desirable procedure for handling IC devices.
Another device for handling a stack of JEDEC trays is the Mühlbaur integrated packaging sleeve or stacker. This device has a base plate and an L-shaped leg projecting from each corner of the base plate. It is expected that the Mühlbaur sleeve is operated by placing the sleeve over a stack of JEDEC trays such that the base plate contacts the IC devices in the top JEDEC tray, and then inverting the tray stack and the sleeve so that the JEDEC trays are carried upside down. To load the trays onto a processing machine, it is thus expected the sleeve is reinverted to right the tray stack, and then the sleeve is removed from the tray stack.
Although the Mühlbaur handling sleeve is an improvement over banding JEDEC trays together, it also suffers from several drawbacks. One expected drawback is that the JEDEC trays can fall out of the sleeve if it is dropped or tipped over. Another expected drawback of the Mühlbaur sleeve is that a JEDEC tray can be removed and lost because the trays are not secured to the sleeve. Therefore, even though the Mühlbaur sleeve is an improvement over banding JEDEC trays together, it is also expected to have several drawbacks.